An inspection of areas or spaces to which access is restricted is necessary in many industries and technical fields. Some simple examples in FIG. 7 illustrate the problem of access restriction. FIG. 7A shows a simple wall or structural component W1 of a considerable size such that it might be difficult to easily inspect the backside thereof, for example if the wall W1 is quite high and only accessible from the top T. FIG. 7B shows another example of a wall W2 to which access is restricted because the back side of the wall is accessible only from one side A whilst the inner space (hollow space) is access-restricted on three other sides B, C and D because of solid walls. Whilst the front surface of the wall W2 maybe visually (or e.g. via infrared sensing or laser sensing) inspected to detect for example mechanical defects, it is difficult to inspect (or analyze) the back side of the wall W2 because the opening A might not be wide enough for a human being to crawl into it or the wall W2 might simply be too high such that it would at least be cumbersome to a person to climb up the wall on one side and struggle down the other side if the side B was accessible (as discussed with reference to FIG. 7A.
There may be also other reasons why access to certain areas or spaces behind the wall W1 or W2 is restricted. For example, the interior space may be polluted with hazardous gases such that a human being must not enter the restricted space for health reasons. It could also be that fire has developed inside the space or behind the wall and this does not allow immediate access. In such a case, the inspection might not simply relate to inspecting the structural component or the inside wall itself but to inspecting the interior space as to whether or not there is trapped a human being who needs assistance.
In cases of such area or space access restrictions, an inspection device, for example a camera, must be inserted into the space differently. Conventional solutions, for example in the field of pipe inspection, comprise the use of a small robot crawling into the piping or into the space to which access is restricted for human beings. Such a robot can be remote-controlled and may be equipped with a camera. For smaller spaces, it might be sufficient to fix an inspection device to the end of a holding rod and then to physically move around the inspection device by moving the holding rod.
In the aerospace industry, inspection of various structural components is essential before, and in particular, after assembly and during maintenance. For example, in the aircraft many access-restricted areas exist as hollow spaces in the wings or elsewhere in the fuselage. In addition, the inner mechanical structure of a wing is quite complicated and involves various different support structures. In such a case, typically a manhole is provided somewhere to provide access to the inner space and a human being crawls into this access-restricted space, for example into a wing or a tank after degassing. On the other hand, exactly because the wing comprises complicated support structures inside it is also not easily possible to have a robot driving around inside the wing for inspection.